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The enrichment of heavy iron isotopes in authigenic pyrite as a possible indicator of sulfate-driven anaerobic oxidation of methane: Insights from the South China Sea
Lin, Zhiyong1,3,4; Sun, Xiaoming1,2,3,5; Lu, Yang2,3; Strauss, Harald4; Xu, Li2,3; Gong, Junli1; Teichert, Barbara M. A.4; Lu, Rongfei2; Lu, Hongfeng6; Sun, Weidong7; Peckmann, Joern8,9
2017-01-20
Source PublicationCHEMICAL GEOLOGY
Volume449Pages:15-29
SubtypeArticle
AbstractSulfate-driven anaerobic oxidation of methane (SO4-AOM) and organiclastic sulfate reduction (OSR) in marine sediments commonly lead to the precipitation of authigenic pyrite with characteristic sulfur isotopic compositions. Yet, no reports on the iron isotopic composition of SO4-AOM generated pyrite exist to the best of our knowledge and the processes controlling the distribution of iron isotopes during this biogeochemical process are not understood. To investigate the mechanisms involved in iron isotope fractionation during SO4-AOM, we analyzed the isotopic composition of authigenic pyrite from two seafloor sites (HS148 and HS217) in the Shenhu gas hydrate area, South China Sea. The delta Fe-56 values of pyrite were found to vary from -0.349 parts per thousand to +0.267 parts per thousand in core HS148, and from -0.793 parts per thousand to +0.178 parts per thousand in core HS217 (relative to average igneous rock) with distinct trends towards higher values with increasing burial depth in both cores. The delta Fe-56 values correlate positively with the extent of pyritization (Fe-py/Fe-HR) derived from a sequential iron extraction procedure. OSR was found to drive early diagenetic pyrite formation at shallow depth, resulting in relatively Fe-56 depleted pyrite. Peaks in the extent of pyritization of 0.45 and 0.47 at ca. 6 and 7 m below the sediment surface, respectively, correlate with high delta Fe-56 and high delta S-34 values, and are interpreted to reflect periods of enhanced SO4-AOM in paleo-sulfate methane transition zones (SMTZs). The great variability in iron isotopic composition and the observed trends are best explained as a function of the availability of dissolved sulfide, reflecting sulfide formation by OSR and SO(4)AOM. The successive conversion of reactive iron to pyrite via sulfidization apparently resulted in the enrichment of Fe-56 in the iron reservoir upon the preferential consumption of isotopically light iron, leading to the formation of successively Fe-56-enriched pyrite especially at or in close proximity to the SMTZ. Therefore, we hypothesize that the combined enrichment of heavy iron isotopes and S-34 in authigenic pyrite is a possible tracer of SO4-AOM in modern and ancient sedimentary sequences. (C) 2016 Elsevier B.V. All rights reserved.
KeywordIron Isotopes Pyrite Sulfur Isotopes Sulfate-driven Anaerobic Oxidation Of Methane South China Sea
DOI10.1016/j.chemgeo.2016.11.032
Indexed BySCI
Language英语
WOS IDWOS:000393001800002
Citation statistics
Document Type期刊论文
Version出版稿
Identifierhttp://ir.qdio.ac.cn/handle/337002/136346
Collection深海极端环境与生命过程研究中心
Affiliation1.Sun Yat Sen Univ, Sch Earth Sci & Geol Engn, Guangzhou 510275, Guangdong, Peoples R China
2.Sun Yat Sen Univ, Sch Marine Sci, Guangzhou 510006, Guangdong, Peoples R China
3.Guangdong Prov Key Lab Marine Resources & Coastal, Guangzhou 510006, Guangdong, Peoples R China
4.Westfal Wilhelms Univ Munster, Inst Geol & Palaontol, D-48149 Munster, Germany
5.South China Sea Bioresource Exploitat & Utilizat, Guangzhou 510006, Guangdong, Peoples R China
6.Guangzhou Marine Geol Survey, Guangzhou 510760, Guangdong, Peoples R China
7.Chinese Acad Sci, Inst Oceanol, Ctr Deep Sea Res, Qingdao 266071, Peoples R China
8.Univ Hamburg, Inst Geol, D-20146 Hamburg, Germany
9.Univ Wien, Dept Geodynam & Sedimentol, A-1090 Vienna, Austria
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GB/T 7714
Lin, Zhiyong,Sun, Xiaoming,Lu, Yang,et al. The enrichment of heavy iron isotopes in authigenic pyrite as a possible indicator of sulfate-driven anaerobic oxidation of methane: Insights from the South China Sea[J]. CHEMICAL GEOLOGY,2017,449:15-29.
APA Lin, Zhiyong.,Sun, Xiaoming.,Lu, Yang.,Strauss, Harald.,Xu, Li.,...&Peckmann, Joern.(2017).The enrichment of heavy iron isotopes in authigenic pyrite as a possible indicator of sulfate-driven anaerobic oxidation of methane: Insights from the South China Sea.CHEMICAL GEOLOGY,449,15-29.
MLA Lin, Zhiyong,et al."The enrichment of heavy iron isotopes in authigenic pyrite as a possible indicator of sulfate-driven anaerobic oxidation of methane: Insights from the South China Sea".CHEMICAL GEOLOGY 449(2017):15-29.
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